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Abstract #27962 Published in IGR 13-1
In vitro fluid dynamics of the ahmed glaucoma valve modified with expanded polytetrafluoroethylene
DeCroos FC; Kondo Y; Mordes D; Lee MR; Ahmad S; Asrani S; Allingham RR; Olbrich KC; Klitzman BCurrent Eye Research 2011; 36: 112-117
Purpose: Long-term intraocular pressure reduction by glaucoma drainage devices (GDDs) is often limited by the fibrotic capsule that forms around them. Prior work demonstrates that modifying a GDD with a porous membrane promotes a vascularized and more permeable capsule. This work examines the in vitro fluid dynamics of the Ahmed valve after enclosing the outflow tract with a porous membrane of expanded polytetrafluoroethylene (ePTFE). Materials and Methods: The control and modified Ahmed implants (termed porous retrofitted implant with modified enclosure or PRIME-Ahmed) were submerged in saline and gelatin and perfused in a system that monitored flow (Q) and pressure (P). Flow rates of 1-50 (mu)l/min were applied and steady state pressure recorded. Resistance was calculated by dividing pressure by flow. Results: Modifying the Ahmed valve implant outflow with expanded ePTFE increased pressure and resistance. Pressure at a flow of 2 (mu)l/min was increased in the PRIME-Ahmed (11.6 (plus or minus) 1.5 mm Hg) relative to the control implant (6.5 (plus or minus) 1.2 mm Hg). Resistance at a flow of 2 (mu)l/min was increased in the PRIME-Ahmed (5.8 (plus or minus) 0.8 mm Hg/(mu)l/min) when compared to the control implant (3.2 (plus or minus) 0.6 mm Hg/(mu)l/min). Conclusions: Modifying the outflow tract of the Ahmed valve with a porous membrane adds resistance that decreases with increasing flow. The Ahmed valve implant behaves as a variable resistor. It is partially open at low pressures and provides reduced resistance at physiologic flow rates.
B. Klitzman. Box 3906, Duke University Medical Center, Durham, NC 27710, United States. klitz@duke.edu
Classification:
12.8.2 With tube implant or other drainage devices (Part of: 12 Surgical treatment > 12.8 Filtering surgery)
